The present invention relates to a regenerative or speed-up valve which operates to enhance or speed up the extension of a reciprocating cylinder.
Many valve arrangements for speeding up the extension of a double-acting cylinder are known in the prior art. One type of such speed-up valve includes a single shuttle or spool member which is movable within a ported valve housing. This type of speed-up valve is described in U.S. Pat. Nos. 2,890,683; 2,590,454; and 1,812,587. However, the single shuttle type valve is subject to a failure condition wherein a rapid pressure buildup in the rod end of the cylinder (due to heavy loads on the cylinder) may prevent or delay the shuttle from shifting to the regenerative or speed-up mode wherein fluid is recirculated from the rod to the head end of the cylinder. In order to solve this problem, more complex or compound speed-up valves have been proposed which utilize a combination of separate check and shuttle valves. Such compound speed-up valves are disclosed in U.S. Pat. Nos. 4,194,436; 4,144,947; 3,654,835 and 3,568,707, for example. However, such compound speed-up valves have been costly, complex and bulky due to the physical arrangements of the separate shuttle and check valve elements.